1. Field of the Invention
The present invention generally relates to electronic circuits and, more specifically, to the transmission of digital data between two circuits via a conversion system. The present invention more specifically relates to the authentication of a transmission in the case where the two circuits do not use the same transmission protocol and use an interface or conversion circuit. The present invention more specifically applies to master-slave type transmission systems.
2. Discussion of the Related Art
Many systems of conversion or interface between communication buses adapted to different protocols are known.
For example, U.S. Pat. No. 6,066,964 describes a dynamic bus in which a communication can be established on one phase or the other of a clock signal.
According to another example, US patent applications 2010/017553 and EP 246287 describe a system of interface between a twin-wire bus and a single-wire bus exploiting the two half-periods of the clock signal of the twin-wire bus by placing the data on a first half-period and a wait pattern on the other half period.
Other mechanisms for converting a communication between circuits using different protocols, and thus an intermediary conversion circuit, are known.
In a master-slave transmission, it is often desirable for the slave circuit to be able to authenticate the master circuit and conversely, be it to indirectly protect the transmitted data or to authenticate the circuits or the data. Such mechanisms generally use symmetrical or asymmetrical cryptography algorithms.
The implementation of such mechanisms is generally not a problem when both circuits are connected on a same bus. However, in the presence of an interface or communication protocol conversion circuit involving an additional circuit, usual authentication mechanisms are not adapted.
In particular, in the case of a master-slave authentication, the converter may alter, transparently for the master and the slave, the content of the frames which transit through it, and thus distort the authentication data.
In other cases where the authentication relies on the converter-slave connection or on the master-converter connection, the system may be deceived by the substitution of a fake master or a fake slave.